If SMART is kind of hard to get used to (I think I'll be fine though), Going Heavy is still a fun option by the looks of it, since they move slower, they can synchronise their movements and positions more easily. (covering all angles, surrounding stuff, being ready to protect each other.)
What's more, lets not forget about the "Cool Abilities", Heavies have more pips.
Basically, going Heavy helps with the stuff I think Brink is really about.